1. Technical Field:
The present invention relates to improvements in methods and apparatus for brushing teeth and, more particularly, to toothbrushes having bristles that rotate relative to the brush head in response to linear reciprocation of the brush handle.
2. Discussion of the Prior Art:
It has long been recognized to be advantageous to apply a rotary brushing action to teeth to remove deposits that build-up on tooth surfaces, particularly adjacent the gum line. The desired brush rotation is about an axis perpendicular to the tooth surface and, for the usual toothbrush configuration, is approximately perpendicular to the brush handle. Hand manipulation of a conventional toothbrush to effect this desirable rotary brushing action is difficult at best, particularly in view of the small surface area to be cleaned and the resulting small radius of curvature of movements of the hand required to accomplish the necessary brush strokes. Powered toothbrushes have been employed to accomplish the desirable rotary brush action but have not achieved significant commercial success, primarily because of the reluctance by consumers to place a powered implement in their mouths. Examples of such powered toothbrushes for effecting rotary brush action of the type described are found in U.S. Pat. Nos. 1,265,536 (Sharps), 1,947,324 (Zerbee) and 4,274,173 (Cohen).
In point of fact, consumers are most comfortable with nonpowered toothbrushes requiring longitudinal reciprocation of the handle to effect brushing. The present invention is concerned with providing an efficient and inexpensive non-powered (i.e., operated solely in response to movement of the user's hand) technique for converting longitudinal brush handle reciprocation to the desired cyclical rotational brush strokes. In this regard, there have been a number of commercially unsuccessful attempts to accomplish this desirable result. For example, in U.S. Pat. No. 1,557,244 (Domingue), there is disclosed a plurality of brush elements mounted in a brush head by means of toothed pinons that are caused to rotate by longitudinal reciprocation of a rack secured to the brush handle and extending into the brush head. However, in order to use this brush, the brush head must be held stationary with one hand while the handle is reciprocated. Such two-handed operation has not achieved acceptance among consumers, most likely because of the difficulty involved in holding the brush head stationary while cleaning teeth located in the back and sides of the mouth.
In U.S. Pat. No. 1,620,330 (Douglass), plural brush sections, each symmetrically disposed about respective axes, are mounted on the brush head to be freely rotatable about those axes relative to the head. However, there is no mechanism provided for positively rotating the brushes in response to longitudinal reciprocation of the brush handle. In fact, true longitudinal movement of the brush handle creates purely radial, as opposed to tangential, not forces on the rotatable brush sections so that there is no turning force applied thereto. Accordingly, in the absence of some mechanism for positively converting the longitudinal forces to rotational forces, there is negligible rotation of the symmetrically mounted brush sections.
In U.S. Pat. No. 1,212,001 (Baxter) there is disclosed a toothbrush having plural brush sections mounted eccentrically on the brush head for pivotability, between stops, about respective axes. Once again, there is no positive mechanism for rotating the brush sections; rather, the frictional engagement between the ends of the bristles and the surfaces of the teeth provides the force that effects pivoting of the brush sections during the initial portion of each linear stroke of the brush handle. While that pivoting action is taking place, the bristle ends flex but move very little, if at all, across the teeth. It is only after the brush sections reach the pivot stops that the bristles move across the teeth, and such movement is linear, in the direction of handle movement, not rotational. Thus, although the brush sections pivot with each change in handle direction, the bristles do not apply the desired rotary brush strokes to the teeth.
There are other prior art toothbrushes wherein longitudinal movement of the brush handle is intended to be converted into some other degree of motion in the brush itself. For example, U.S. Pat. No. 2,660,745 (Yusko) discloses a toothbrush wherein the entire brush head oscillates about the longitudinal axis of the handle in response to longitudinal reciprocation of the handle. The result is an up and down movement of the brush bristles across the surfaces of the teeth. This brushing action was, at one time, considered to be efficient but in recent years has fallen into disfavor among dental professionals.
Still other toothbrushes having bristles that are movable in relation to the handle or head are found in the following U.S. Patents.
______________________________________ U.S. Pat. No. Patentee ______________________________________ 618,690 Ter Laag 1,257,883 Kone 1,911,973 Ruse 2,160,836 Davids 2,184,850 Schloss 2,188,449 Stewart 2,290,454 Steinberg 2,411,610 Aaron 2,799,878 Brausch 2,917,759 Siampaus 3,110,918 Tate, Jr. 3,214,776 Bercovitz 3,994,039 Hadary 4,638,520 Eickmann 4,682,584 Pose 4,766,630 Hegemann ______________________________________
These patents all disclose devices having different brush stroke action than the desirable rotary action described above, but are of general interest in that they show a wide variety of actuating mechanisms for achieving brush movement.